How much is enough?

Studies show that four 30-second sprints on a bike, 2-3 times a week can help to improve insulin sensitivity. But the exercise must be flat out.

• Ten minutes

The minimum amount of activity recommended by the Government if you are overweight, sedentary or both. You should aim for three bouts a day.

• 15-20 minutes

For fitter people who are short of time, a 20-minute workout can produce notable fitness benefits. Government recommendations also suggest that adults do muscle-strengthening exercise each week; a 20-minute weights session is ideal.

• 30 minutes

The daily target (at least five days a week) for anyone looking to maintain health and weight. Your 30 minutes can be cumulative, but you can also aim to perform 30 minutes of continuous activity on at least two days.

• 45 minutes

Aim for this duration if you are looking to improve your fitness as well as lose some weight. Increasing the intensity of your session can help you to reach your goals more quickly. Three 45-minute sessions of vigorous exercise weekly are equivalent to six 45-minute sessions at a sedate pace.

• 60 minutes plus

Some hour-long sessions are necessary if you are in training for an endurance event or looking to get fitter. Most gym classes last for 45-60 minutes, but be aware that many people who slot their exercise into a single session are less active for the rest of the day.